High Quality AlN Layer Grown on Patterned Sapphire Substrates by Hydride Vapor-Phase Epitaxy: A Route for Cost Efficient AlN Templates for Deep Ultraviolet Light Devices.

We report the characteristics of AlN epilayers grown directly on cylindrical-patterned sapphire substrates (CPSS) by hydride vapor-phase epitaxy (HVPE). To evaluate the effect of CPSS, we analyzed the threading dislocation densities (TDDs) of AlN films grown simultaneously on CPSS and flat sapphire substrate (FSS) by transmission electron microscopy (TEM). The corresponding TDD is measured to be 5.69 x 10 cm for the AlN sample grown on the CPSS that is almost an order of magnitude lower than the value of 3.43 × 10 cm on the FSS. The CPSS contributes to reduce the TDs originated from the AlN/sapphire interface via bending the TDs by lateral growth during the coalescence process. In addition, the reduction of direct interface area between AlN and sapphire by CPSS reduce the generation of TDs.